The puzzle of life and how it has been put together

THE DAWN OF LIFE.

The first beams of the rising sun, and the first grey light of the morning, tell us of the coming day; but we cannot even think of the dawn of that far-off day in the Earth’s history, when no voice of man or beast was heard, and no trees or grass covered it, without solemn wonder at the immense distance that day is from us. A thousand ages are in the sight of the Creator but as yesterday, and the period of man’s existence is only a moment compared to that of the lowly creatures which built up this World for him. In the first seas and on the land nothing was heard but the rushing of waters and the roaring of the fires of volcanoes.

It is impossible to be quite certain whether the first living things were animals or plants; but I think it most likely that very simple plants grew first, and that very simple animals came after or with them. Among the first of these, or perhaps the very first, were some small animals called Eozöon, which means the “life-dawn animal,” and with them grew some simple plants. On the banks of the St. Lawrence river in Canada there is a great bed of rock called the Laurentian rocks, made almost entirely of the tiny remains of the “life-dawn animal,” which, when we look at them through a microscope, are found to possess nearly the same structure as some lowly organized shells living in the seas now. These rocks are found in many parts of the world besides—in Eastern America, Bavaria, Scotland, and Norway; and in some places their thickness has been estimated at thirty thousand feet, or nearly six miles, or one hundred times as thick as St. Paul’s Cathedral is high! These little creatures you see were at work over a great part of the Earth’s surface, and you may fancy how many thousands of thousands of years it took them to build up these rocks. The “life-dawn animal” is far older than the chalk-building foraminifera, and so far as we know it lived alone in its seas. There were none of the beautiful twisted ammonite shell-fish, nor the shark-like fishes of the chalk seas. The eozöon was the only kind of living creature, the “lord of creation” for the time; and though storms raged in the seas it inhabited, the water was so deep that it lived on undisturbed. When you are able to use a microscope you will be able to see the traces left by these tiny animals in what is now hard stone.[1]

Life began in a very small way: there were none of the great land animals we have now; but these seemingly insignificant builders were at work so long that they made the immense rocks I have told you of. But this is not all. About this time some very simple plants grew on the land, and were carried down by the rivers and formed deep beds. After a long time these became covered up with different earths and were turned into the substance called “black-lead,” which you use in drawing pencils. But this is not really lead; it is almost pure carbon—in fact, the oldest kind of coal—so old that it will not now burn like coal, and is entirely made up of fossil plants crushed out of shape, so that we cannot now trace their forms, as we can the plants of the coal. When then you next take up a drawing pencil it will be easy to remember that the black substance which marks the paper was once a living plant, now changed by heat and pressure into almost pure carbon. As the name eozöon has been given to the “life-dawn animal,” I will give this black-lead the name of Eodendron, or the “dawn-plant.”[2]

Two very simple forms of life then occupied the earth and sea at the earliest time when anything at all was living, and strangely enough we use the dead bodies of both of them. We build houses of the rocks the eozöon laid down at the bottom of the sea, and the beautiful art of drawing is carried on with the carbon from the first plant life of the world—the eodendron.

I must take you away presently to the coal, and sandstone, and chalk, and show you how plants and animals gradually increased in number and size, and fishes began to inhabit the seas, and all living things were slowly going on to greater perfection; for as time went on there was a steady progress from creatures like the eozöon, which had scarcely any power of moving about, to the active, quarrelsome and greedy things like crabs and lobsters which came after them, and the gigantic ferns of the coal beds. The peaceful “life-dawn animals” drew their food from the vegetable substances dissolved in the waters, though they perhaps also lived on animals still smaller than themselves; but, by-and-by, creatures, which must have been monsters to them, swarmed in the seas and devoured their smaller companions wholesale; and in time the Earth became very much the same as it is now, a place where the struggle for life is always going on. It is certain that animals have fed upon one another from the very beginning; but this is no doubt a wise law of the Creator to prevent them from increasing too fast, as they would do if all that were born lived, and none were destroyed.

We know much less about the vegetation—the plants and grasses—of the early ages of the world than of the animals; because plants rot away faster than bones and shells, and, besides, are less likely to be found in places where they would be preserved. A dead tree might be eaten up entirely by insects, as the white ants eat up fallen trees in a short time in tropical countries, and what is left of them crumbles away to fine powder and mixes with the soil. Immense trees are thus devoured now by millions of tiny insects no longer than your thumb nail, in India and Australia. No such thing as a whole and perfect fossil tree with every twig and leaf has been found; but then the coal beds are really great forests which have been buried for so long a time that they have quite altered in appearance. Still, among these coal beds we often find the bark, fruit, stems, and branches of trees very much like firs, and ferns, and huge club-mosses, which have the same shape they had when living, though they are quite black, and burn exactly like coal.

But there were plants long before the coal forests lived, and many fossil sea weeds are found in the old sandstones and limestones in Wales and other places.[3] The Old Red Sandstone, whose position you can see below the coal in the table of succession of formations, page 42, does not give us many fossil plants, though fishes and shells are common. This rock is found in Scotland, Herefordshire, Devonshire, and Ireland, as well as other places, and is often more than 2,000 feet thick. It was not all formed in salt water we know, because many of the fossil fishes and shells it contains are fresh water kinds. It must all have been made of the pieces of still older rocks worn away by rivers and settled like a sediment in immense lakes, some of which were fresh water. Then, after the Old Red Sandstone, came a time when the limestones below the coal were laid down at the bottom of a vast sea, and here the remains of land plants are of course few. Then it seems there must have been a very long time when there were large continents all over the world raised above the seas, but not very much, and on these the forests grew which afterwards became coal fields. Until this time the plants had been mostly water weeds, reeds, rushes, and sea weeds, and it was not until England and Ireland became one continent, as they were once and covered with woods, that the great period of vegetation began.

The growth of plants was then most wonderful; but although coal is found in many different parts of the world, it was not all formed at one time, and though it is plentiful in England and Wales, Scotland, Ireland, France, Belgium, Russia, Hungary, Australia, New Zealand, China, and Borneo, it is older in some countries than in others. It is fortunate, however, that this useful material was made in Nature’s workshop in so many different countries, or it would have to be carried from one to another. The coal forests were not the same trees as we have now—oaks, elms, ashes, limes, and so on. Most of them had rather hollow trunks and splendid waving tops like ferns and reeds, though there were some like our fir-trees.

If you lie down in the long grass before it is mown, and look through the stalks and fancy yourself an inch high only, you will have some idea how the coal forest would have looked if you had lived then. But there were no human beings on the Earth then, and I do not think there were any large animals, at least none have been found in the coal itself, except in Switzerland, where a few bones of the mammoth (an ancient elephant) and of the rhinoceros have been discovered in the much newer beds of coal, and also those of a large reptile like a crocodile in the coal beds of Ohio in America.

In such immense forests insects must certainly have been plentiful, and some of the fossil bodies of beetles, dragon-flies, and spiders, have been preserved, and a few tree lizards.[4] Of course the edges of the coal forests were washed here and there by the salt sea, and there must have been some fresh water rivers and ponds, for we find both fresh and salt water shells in these beds. It was almost dark in these forests, so thickly did the plants grow together. There were enormous club-mosses close together and as high as most houses, with their leaves interlaced making a complete network to shut out the sun. But the sun which shone on the forests was warm, and the air which went through them was soft, or they would not have grown so wonderfully. Indeed, there can be no doubt that the climate of northern regions was once much warmer than it is now. A thick bed of coal was discovered by the Arctic Expedition in 1875-6 actually within five hundred miles of the North Pole, where the ice on the sea is now thirty or forty feet thick![5] The forest which formed this coal could only have grown in a temperate climate, and there are no forests there now; it is so intensely cold they could not live. There must then have been a great change in the climate of the Arctic regions since that coal was living vegetation. The few plants and mosses which can live there now are of a very different and more hardy kind than those of the coal forests.

If you look at the engraving facing page 64, you will see a drawing of one of the tree ferns with its delicate fronds which grew so abundantly in the coal forests, and there are many other plants, some like the common “mare’s tails,” or calamites, growing in shallow ponds and ditches now—only the “mare’s tails” or calamites of the coal forests were as high as poplars.[6] You can imagine what a splendid sight these forests of ferns, club-mosses, and “mare’s tails,” must have been, and what a multitude of beautiful insects and butterflies must have flitted about in them; but their frail bodies have almost all perished, so that we know very little of the animated creatures of the time.

Besides several sorts of coal both soft and hard there is a substance called “lignite,” which is scarcely wood and scarcely coal, of a brown colour. In fact, lignite is wood almost turned to coal, and it has helped us to learn that coal was once living wood; but it is not nearly so old as the coal. Then again there is the beautiful substance called “jet” used for making bracelets. This is a kind of fossil gum or pitch dropped from the trees while they were growing, and, though different in colour, it is much the same in kind as amber. Amber is often found with flies, spiders, and small leaves imbedded in it. When this fossil resin or gum was flowing out of the ancient pine-trees, and was quite sticky, flies settled upon it and became entangled in it, and as more of the gum flowed out they became quite covered. Then the gum dropped from the tree and hardened, and it is now found in lumps on the shores of the Baltic Sea, and in beds of sand and clay with fossil wood. It is of a beautiful bright yellow colour, and beads for necklaces and other ornaments are made out of it.

If we arrange the things we have been talking about in order, the oldest first, they would come thus: plumbago or black-lead—or, as I have called it, eodendron, “the life-dawn plant”—first, then hard coal, then soft coal, then lignite and jet, then bog oak and peat. But I must tell you something about bog oak and peat. In many of the swamps and bogs of the World the trunks of dead trees are found, which have become quite black and almost like lignite, because they have been buried so long. Thus, in the bogs of Ireland oak trees are often found, and they were most likely living when the reindeer inhabited Ireland. This old bogwood is made into beads for necklaces and other ornaments. Peat is a partly decayed vegetable substance, with beautiful little plants growing on its surface, and is really coal in its infancy. It is found all over the world more or less in wet places, and consists of the roots and stems of mosses and reeds, some of which are like the gigantic plants of the coal period, but very small in comparison. I have no doubt that in time some of these peat bogs may be turned into coal if they sink down and become covered with other earths, but at present they are all on the surface and so soft that they are dangerous to walk upon because one may sink in and be smothered.

This, as far as we can trace it, is a sketch of the history of vegetable life on our Earth. We will go back to the coal for a moment and see what the animal life of that time was. The seas of the time of the coal forests were sometimes shallow, sometimes deep, and in the limestone rocks of the oceans which separated the great continents of that time there is a record of the inhabitants of the seas. The land plants were of more than 1,000 different kinds, and there were more than 200 kinds of fishes in the waters, and corals, shells, and small crab-like animals innumerable. The fishes were fellows with terrible teeth, and their bodies were covered with strong hard scales. One of these fish was thirty feet long, and there were others of considerable size. It is curious that the fishes of this time remind one of reptiles (lizards and crocodiles), just as the birds of a future time seem to have something of the reptile about them, as you will see by-and-by.

I dare say you have remarked while reading that all the plants and animals of the early ages of the world seem to be made on a simple plan, and as the Earth grows older they become more perfect, and this is just what I want you to take notice of all through. The plants of the coal period, you have seen, were nothing like so perfect in construction, beautiful as they were, as the forest trees of the present time, neither were the animals so perfect as those living now. There has been progress, step by step, throughout the vegetable and animal creation; and, though many of the lower forms of the early ages exist now, there are others far superior to them which did not exist then: but all this will come in “The Animal Part.”

About the middle of the Earth’s age came the wonderful period of vegetation which gave us our coal, and after that there was a great and busy time, when huge reptiles and reptile-like birds, and then true birds, made their appearance. But that belongs to the next part of the “puzzle of life.”

If we look with astonishment at the coal forests, we may also well think of them with thankfulness. Here is the sunshine of past ages stored up for our use, and we bring it out again to warm ourselves, cook our food, make all our iron things, and drive our steam-engines! Can any romance be finer than this, that we are carried across to America and India and Australia in steam-boats driven by the “fossil sunlight” of ages and ages past, and whirled along at sixty miles an hour over iron rails by the same stored-up strength?

If you doubt this, think of living trees. Do they not live by the air and sunlight? Will they grow without these? They spread their branches and leaves to gather the warmth and light from the air, and when they are cut down and dried, and you put a match to the wood, all the old warmth and light come out again; and we know that the coal is only fossil wood. Our Creator wastes nothing. Even when there were no people living to rejoice in the sun, He thought of those people who should come in time, and not one of the fiery rays of the fierce sun was lost. These mighty forests were sent to gather it, and when they had died down they sank below the surface and were covered from the air, that none of their light or heat should escape.

In such forests it is strange that there were no birds, especially as there were swarms of insects, and no doubt abundance of worms. But no bone of bird or any trace of feathered songster of these lovely groves has yet been found. Little lizards chased flies and beetles up and down the stems of the club-mosses and ferns, and larger reptiles lurked in the long damp grass under the shade. The pools and ponds were filled with curious fishes, and reefs of beautiful white coral fringed all the shores of the seas.

But the Earth was not fit for the habitation of man. The fruits of the trees were not such as he could have eaten, and their wood was not hard enough to build houses of. Still it was being got ready for him, and not a leaf waved uselessly in the bright, warm air, and not a tree fell to the ground, but it was to be turned into coal, and to come forth again one day a hard black lump, without any of its former beauty, but to give back the light and heat it had gathered from the sun ages and ages ago.

Many periods in the Earth’s history have passed since the coal period, and in every one of these the trees have been increasing in perfection, though there have never since been such great numbers of a few kinds growing. When we come to the more lately formed beds of earth we begin to find the cypress, willow, ash, oak, elm, and other forest trees which are living now. The trunks of these trees, blackened by age, lie buried in peat bogs and swamps all over Europe. The mighty Mississippi river brings down immense quantities of dead trees, and as these sink to the bottom near its mouth they are forming future coal beds. Along the coast of Norfolk and Suffolk, too, and stretching far away under the German Ocean, is an old English forest. In some places the trunks of the buried trees may be seen standing upright just where they grew. The nets of the fishermen are continually bringing up pieces of wood, roots, and seeds; and when the sea washes away the soft cliffs here the bones, teeth, and tusks of the elephant, rhinoceros, hippopotamus, and other large animals which inhabited this forest, may be seen in great numbers.

Down below the waves of ocean have these woods sunk with all their once living creatures, and though you may suppose that it must have been very long ago that they grew, they are of the same kind as those which now make the hills and valleys of England beautiful.

Sometimes a forest must sink very fast, for travellers have told us how they have sailed on rivers and lakes over the tops of sunken trees, and, looking down into the clear water, have seen the branches waving below—tall trees standing upright at the bottom, and the boats sailing over their tops!

We must now pass on to the living creatures which peopled the Earth, and their story can be told with more certainty than that of the perishable plants which clothed the surface of the ground, and, while they rendered it beautiful, also served as food and shelter for innumerable animals, and have become so useful to us as coal, lignite, black-lead, and other productions of ancient forests.